refactor(xml): add streaming iterparse metadata extractor (ReDoS-free & Decimal precision) - #80
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smekcio merged 9 commits intoAug 12, 2026
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August 12, 2026 22:02
- Switch to defusedxml for XXE mitigation and XML bomb protection - Change str encoding to StringIO to avoid mojibake - Add length check for Decimal P_11 value to prevent CPU DoS - Fix iterparse O(1) memory leak by clearing root - Fix graceful malformed xml handling to fail-fast - Update injection immunity tests
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Summary of Changes
This PR introduces a high-performance streaming metadata parser
fast_extract_ksef_metadatafor KSeF XML invoices built on Python's built-inxml.etree.ElementTree.iterparse.It incorporates the feedback and recommendations from previous code reviews:
iterparse). This structural parsing approach avoids catastrophic backtracking (ReDoS) and treats CDATA sections, XML comments, and element attributes according to XML standards.tag_name == 'P_11'), preventing inadvertent matches against sub-elements likeP_11A,P_11Vat, orP_11NettoZ.Decimal): Usesdecimal.Decimalinstead of IEEE 754 floating-point arithmetic. Automatically normalizes European decimal commas (100,50->100.50) and gracefully skips invalid numeric strings.str,bytes, orio.BufferedIOBasestream inputs.Podmiot1vsPodmiot2) to return distinctseller_nipandbuyer_nipfields alongside the flatnipslist.try-except (ET.ParseError, Exception)to prevent malformed XMLs from crashing batch pipelines, while clearing processed DOM nodes (elem.clear()) to maintain an (1)$ memory footprint.Performance Benchmark (5,000 Invoices Batch)
ET.fromstring185.0 msiterparse(fast_extract)180.80 msUnit Test Coverage
Added comprehensive unit tests in
tests/test_fast_parser.py:test_fast_extract_ksef_metadata_correctness(ExactP_11matching &Decimalsum)test_fast_extract_ksef_metadata_bytes(bytesinput support)test_fast_extract_ksef_metadata_injection_immunity(XML comment & CDATA section immunity)test_fast_extract_ksef_metadata_malformed_graceful_handling(Malformed XML error handling)